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You are here: Home Events Dr Vincent Roucoules "Plasma Polymers For Designing Reversible Mechanoresponsive Bioactive Surfaces"

Dr Vincent Roucoules "Plasma Polymers For Designing Reversible Mechanoresponsive Bioactive Surfaces"

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Institut de Science des Matériaux de Mulhouse, France

What
  • Seminar
When May 30, 2012
from 02:15 PM to 03:15 PM
Where Hörsaal Makromolekulare Chemie, Stefan-Meier-Str. 31, Freiburg
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Plasma assisted polymer synthesis draw a considerable attention not only because of its versatility and flexibility but also because of its economic and ecological advantages. When an electric field is applied across a vapour or gas filled chamber of a suitably "polymerisable" compound (termed "monomer"), it ionizes a fraction of the molecules and generates electrons, ions, radicals, photons and molecules (on both ground and exited state) within the gas plasma. Polymer thin film growth then occurs within this environment. Traditionally, plasma polymers lead to high cross-linked macromolecular structures which differ from the precursor structure used. In order to counterbalance this phenomenon, we focus our researches on pulsed plasma polymerization. This entails modulating the electrical discharge on the ms-ms time scales and comprises two distinct reaction regimes corresponding to the on- and off- periods. It is expected that plasma polymerization could be proceeded during the ‘on’ period and also during the ‘off’ period. But a conventional polymerization such as radical addition reaction takes place during the ‘off’ period discharge. This gives rise to extremely high levels of structural retention and incorporation of specific functional groups at the surface. By programming the on/off periods, it is possible to control the desired density of the functional groups at the surface. This variant is used to control variations in the nanometric scale of chemical compositions and physical properties of the material surfaces.

The design of responsive materials and in particular mechanosensitive materials is now thoroughly investigated and it emerges as an extremely hot topic. We present here two examples of mechanoresponsive surfaces designed i) by using plasma polymers as platforms to attach materials sensitive to the mechanical stimuli or ii) by exploiting intrinsic properties of plasma polymers to change their performances under stretching.

The first example concerns chemo- and cyto- mechanoresponsive surfaces which become proteins adsorbent or cell adherent under stretching in a fully reversible way. Our strategy is based on grafting ligands directly on a plasma modified elastomeric substrate embedded in a PEG brush. By stretching the substrate, the ligands become accessible to proteinic receptors. Returning to the non-stretched state, the pressure exerted on the proteins induces their expelling assuring a full reversibility of the process.

The second example concerns the effect of mechanical stimuli on the release of bioactive agents (here antibacterial agent) from a plasma multilayer matrix. Owing to differences between mechanical properties of plasma-polymer thin films and the elastic bulk substrates, tensile strengths generate cracks within the plasma polymer, which might be used as diffusive channels for bioactive substances located between two plasma polymer thin films. The originality of this system is that the aperture of the cracks can be controlled mechanically in a reversible way.

Such surfaces would not only be of fundamental interest but could also present numerous potentialities from a technological point of view.

 

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